After the transportation of freight by railroad from a place of origin to a delivery point or destination, it is all too common and necessary to return the railroad cars empty to the place of origin to be loaded again. In some instances the cars must be returned empty because there is no return load of any kind to be carried. At other times return loads which are available cannot be shipped in the type of railroad cars to be returned to the point of origin. For example, coal cars would not be suitable for carrying a return shipment of a liquid product. Regardless of the reason, moving empty cars is costly, in part because of the absence of a pay load, but also because of the labor and fuel costs involved and the wear and tear on the equipment.
With respect to North America, liquid lading is at times to be transported by railroad from a point of origin to a destination which has a solid commodity, in the form of a particulate or granular material, which is to be transported back to, or reasonably close to, the point of origin of the liquid lading. If cars adapted to carry only liquid or solid lading are used, it is necessary for the return trip in either direction to move the cars empty with the disadvantages already described.
Various solutions to the described problem have been advanced in both the railroad car and highway trailer industries. See, for example, Dunn U.S. Pat. No. 2,323,458; Henderson U.S. Pat. No. 4,403,783; Rollins U.S. Pat. No. 3,495,548; and Freudman et al U.S. Pat. No. 3,583,330. Even though these patents propose various solutions, a need exists for a more improved railroad car which can carry alternate liquid-solid lading in either direction, especially a car which can alternately carry the maximum load of heavy solid lading, or a maximum load of liquid lading, permitted by railroad standards. Additionally, a need exists for a multiple compartment railroad car which can carry simultaneously both solid lading and liquid lading in separate compartments, regardless of whether the goods originate at, or are shipped to, a common area.